Hob



Aug. 17, 1943. J. c. DRADER 2,326,932

, HOB v Original Filed Oct. 21, 1935 2 Sheets-Sheet l INVENTOR Jase (fflrairn J. c. DRADER 2,326,932

HOB

Original Filed 001;. 21, 1935 2 Sheets-Sheet 2 Aug. 17, 1943.

INVENTOR Patented Aug. 17, 1943 1 UNITED STATES PATENT OFFICE '1 2,a2s,932, T

g 3 g g HOB" I Joseph Drader,yDetroit, Mich, assignor to Michigan Tool Company, Detroit, Mich., acorporation of Delaware l p g a Original application October 21,1935,'Seria1 No.

45,879; Divided and this application May 11,. ,7 i939, SerialNo. 273,070 I 3fClaims. (01.295403);

This application is a division-of applicants prior co-pending application Serial No. 45,879, now Patent No. 2,164,643, of July 4, 1939, and relates to a hob for cutting tapered splines; The

invention set forth in applicants prior co-pending application is directed specifically/co the method of forming tapered splines which embodies the hob covered herein.

Principal objects of the present invention include the provision ofan apparatusforforming a tapered spline connection; to provide such a connection in which atapered hub is provided ith spline grooves of varying depth along its length, separated by lands of uniform width; in

which a correspondingly tapered axle is. provided with grooves which are of uniform section throughout their length and are separated by.

lands of varying width; and in which, in assembled relation, the roots of the grooves inthe axle lie parallel to the surfaces ofthelands formed in the hub.

Further objects of th present invention in- I clude the provision of an improved method for forming a splined connection, asabove stated, in

which the grooves in the axle are cut through use of a hob; in which the axle is disposed with its surface longitudinally tangential tome-surface Y 7 of the hob at the point of contact between the hob and the surface, to thereb out grooves,, of

uniform section; and the axesof thehob and of, is automatically provided for by thedifference in peripheral speed between the small end and the large end, thus permittinga uniform rate of rotation of the axle during the cutting operation.

Further objects of thepresent invention include the provision of an improved ground hob particularly adapted to the formationI of the splines in an axle, as above stated, but also adapted to other uses as well, and in which the teeth of the hob are of varying size around the hob; in which the teeth of the hob are divided into finishing teeth and roughing teeth, ,the roughing teeth being of reduced size; in whichthe hob is provided with a double thread corresponding cutting edges in the two threads being in ,diarnet rically opposed relation upon'the hob.

With the above and other objects in vi'ew. whichappear in thefollowingdescription and in the appended claims, an illustrativeandfpree ferred embodiment of the present'invention is shown inthe accompanying drawings, throughout the several viewsof which corresponding reference'characters are used to designate corresponding parts, and in which:

Fig. 1 is a view in end elevation of a hob em- "bodying the present invention;

of the improved splined connection of the present invention; i i

Fig. 6 is a fragmentary view in section, taken along the line 6-6 of Fig. 5; l

Fig. 'Tis a fragmentary view in section, taken along the line l 'l of Fig. 5;

Fig.8 is a fragmentary View in section, illustra the parallel relation. which preferably exists between the roots of the grooves'formed inthe axle, and the surfaces of the lands formed in the hub and; 7 Figs!) and were views illustrative of the relative dispositions of the tool and the work in the preferredpractice of the invention.

The novel features of the present invention are disclosed in the present application as embodied in an improved tapered splined connection, a method of producing such a connection, and an improved ground hob for forming serrations in a tapered object. The tapered spline connection comprises atapered hub, and; a correspondingly tapered axle. The axle and the hub are correspond'ingly serrated toform a slid able but nonrotative connection between them. The serrations m1 the hub constitute a succession of grooves, the depth and section of which increase from the small end to the large end thereof by an amount sufficient to cause the lands between'the grooves to be of uniform size throughout the length of the hub. The hub serrations may be produced in various ways, forming no part of the "present invention. For example, as, will be understood, these serrations may be formed by a broaching operation, the path of movement of the broach being angled to the slope of the tapered surface of the hub by an amount sufiicient to gradually change the section of each groove to the extent just stated.

v Theserrations in the axle are preferably of uniformsection throughout their length. Due

tothe taper of the axle, accordingly, the uniform serrations therein are separated by lands the width of which increases from the small end of the axle to the larger end by an amount depend ent upon the taper of the axle. The axle thus serrated mates in correct splined relation with the hub, the roots of the axle serrations being parallel along their length with thesurfaces of the uniform lands formed in the hub;

According to the present invention, the serrations in the axle are cut by running the axle in synchronism with a hob. The hob and axle axes are crossed at an angle to each anther equal to the helix angle of the hob 'so that, as will be understood, the serrations cut in the axle surface have a zero helix angle,or .are parallel with the axis of the axle. Because of the ta-per'of the axle, it will be understood that the peripheral speed at the smaller end is somewhat less than the peripheral speed at the larger end, and while this variation in peripheral speeda-lon-g :the length of the tapered surface automatically 513'10- duces thecorr-ect variation in widt-lrof the lands which separate the serrations in the axle, -:i-t renders it desirable to modif'y the teeth of the hob so that certain of :the :teeth vperform (Only a roughing vope-ration :others pjerform a finishing operation.

The improved hob of the .present invention embodies two :threads or ihelicall rows of teeth, each row being illustrated as comprising twenty teeth. The vcorresponding teeth the two rows are disposed in diametrically :opposit-e relationship, since, as will be understood, the respective rows of teeth out alternate serrations in the axle. Of the teeth in :each row, those which may for convenience be designated as teeth cub, and-"c are finished to the i'orin ofthe desiredcserraftions, and substantially correspond to the dimensions of the serrations. T-lieremain ing teeth in each row are not finished to-this iorm,-since'suciiteeth perform only a preliminary cutting or roughing operation. f such remaining teeth, teeth cl, e, and g are reduced in size-so that they present -a 'section somewhat smaller than the desiredsection" of the serrations. Preferably also, the teeth last identified are re-c-ut so mat the *iead of the rightsides-thereof is somewhat less' than the lead of the finish teeth a, h, and c, 'aridth'e lead of the left sides thereof is somewhat in excess the finishteeth lead.- The remaining teethin each row, h, "i, i, m, njo, 'p, q, 13's,- and t are of still further reduced section, although the lead thereof may, and "preferably does, correspond to the lead of the finish teeth a, ojandc.

With this relation, as will be understood, the finish teeth a, b, and '0 correspond in functionjin certain respects to thejteeth of a fly cutter, and cut serrations in "the axle which "are of the desired final section and substantially parallel along their lengths to the axis ofthe axle. "The "remaining teeth of reduced section supplenient the action of the finish teeth and perform a preliminary cutting action. The reduction in size thereof "compensate for the unbalance "between the lead of the hob teeth and "the -Varying peripheral speed of the axle, and prevents distortion of the serrations.

It has been found'in the practice of the present which satisfactorily and accurately-mate with the ,7

5 Considering the above mentioned elements in more detail, and referring to the drawings, the completed illustrative tapered spline connection com-prises the hub iii and the axle i2. Hub It is provided with acentral axial opening id, which in accordance with conventional construction, is

a generally circular. The opening it is somewhat larger at one end than at the other, thus providing a uniformly tapered surface. The inner surfaceof'the bore I4 is serrated to provide a 15 succession of grooves I6, separated by lands [8.

As .previouslystated-the grooves IE, while having uniformly angled side faces throughout their length, are deeper at their larger end than at the smaller end, by an amount suiiicient to maintain the lands [8 of uniform width throughout the -breach being angled to the surface of the {opening il by an amount sufficient to provide the desired increasing depth of groove.

The axle i2 is tapered to correspond- .to the taper 0f hub 51 d and the surface thereof is serrated :to provide a plurality of grooves .28 :separated by lands 522. :As previously stated, the g1 eves 20 are of uniform -section throughout eirilengtingand with this irela tionship it will be dmatthe ilands 2 2 increase in Width from the smaller end hi the .ser-ratedsection to the flange end thereof. This relationship, as Well as 18 above described relationship of the grooves 16 :lan'ds =18 of hub i i are clearly illustrated in the comparative views, Figs. 6 and 7.

I-n the a'ssembled spline connection, the grooves 29 in axle [2 are of uniform section, having sides which lie parallel :to the surfa es of the lands 4 8 formed the hub it! which are of uniform section- This relationship is illustrated in the agmentary view,'-1 -ig.'8. it will beeviden-t that 1e surf-ace connection thus provided between the hub-and axle provides a positive drive relation t'here'betweenand eilects a-positive limit to their axial movement. a

'The hobBTL-shGvVn in detail in "1 through 4, and which is preferably used to form the serrations in the ax-le i2, is provided with an ac- =curat-ely dimensioned central opening and 'keyway -3 5,- through w-hich it be secured to 'anaibor for rotation thereby. The hob is providedon "its surface with a 'oloublerow of teeth, theteeth'in one 'row bei-ng designated-a, 0, etc, and the teeth in the other row being designated -a", o, 'c'. It Wiil be understood that the two rows of teeth are du-plicates of each other and that corresponding teeth in the respective rows, such-as teeth a and a, are disposed in diametri'ca'lly opposed relationship. It will also be understood that in operation, the row of teeth including teeth a, b, 0, etc; and the teeth in .the other row, respectively, cut'alternaite serrations inthe surface 'of axle I 2. j

As previously described in a general way, the

, teeth a, b, and c, and the corresponding teeth :10 a invention that the use of a hob constructed in a", b; and c" are ground'to the correct form and .proper,'dimensions of the grooves 2i? to be formed .inthe axle [2. These teeth perform a finishing function, and may be said to function much'as anycutter.

and in practice it isjnot necessary thatthese teeth be ground to accuratetooth form, as they accomplish merely a roughing operation. The

comparative dimensions of the finishing and roughing teeth are illustratedin the fragmentary views of 1iigs.-3 and 4 in which; the dimensions v and 1 respectively, applied to a toothh; are

larger thanthe corresponding dimensions wand eiapplied to one of theteeth d r I "The remaining teeth of each row including teeth h, i and t' are further reduced insize. As previously stated, the leads ofthe last identified teeth 'may correspond to the leads of the finishing teeth (1,1), 0, etc; but the lead of the right hand 7 sides oftheintermediate teeth d, etcQiS'prefer-Q ably somewhat less than such lead, and the leadof the left handsides of the intermediate teeth is preferably somewhat in excess of such 1ead. 7 In operation, the hob 30 is disposed with its v axisat an angle to'the axis of the axle I2, Iequal to the helix angle of the hob, so that the serra-f tions cut' in the axle are'straight or parallel to the axis of the axle; It will be understood that hob 30 and axle l2 are fed into each other radially duringfthe cutting operation, and that s, and t andteeth h, i s

axle I2 is indexed along axially from time to time.

' .to extend the grooves 20 therein to the desired length. As the hob and axle are indexed longitudinally relative to ,eachother, theminimum V spacing. between the, hob axis and the axle surface ismaintained constant, so, that'the Serra tions 'a'relof uniform section throughout "theirl length. As previously stated, due to the ta- A pering surface of axle. t2, the peripheral'speed at the reduced end of the serrated section is somewhat less than the peripheral speed'atthe enlarged end; of the serrated section, and this difierence'in peripheral speed beingprbportional 7 1 i beginning of each-row being smaller than the fin-' ishing teeth at theend of each row, with the 45 teeth at thebeginning of. each row being di'sposedat points diametrically opposite each other. a

to'the taper angle of axle l2, acts 'to automatically bring about the desired increasing width of the lands 22 whenhob 30 and axle [2 are run together. 7

The rate of rotation of axle I2 is such that the average of the abovestated'peripheral speedsiis correctly relatedto the'le'ad'of the rows" of teeth onhob'30. Atpoints onthesurface of axle I25 havingja peripheral speed other than such aver- "age value, a slight unbalance exists betweenthe perip'heralspeed, of the point being out and the,

1 lead of the teeth on the hob 30. Anytendency,

' however, of this unbalance to causethevcuttingf H of irregular grooves ,'is overcome bylimitingth'e finishing action to a relatively few ofthe teeth;

as above described, and reducing the size of he t remaining teeth sufficiently to prevent them Q. from distortingtheserrations, from straight 1 form. The use of such remainingjteeth, however, to perform a roughing operation,"m'aterial ly increases the rate at whichthe-serrations may be cut and thus correspondingly reduces 'the cost ofthecompleted spline connection;

, Although a specific embodiment of the present invention has been described, it will be evigo dent thatvariouschange's-in the method ofpracticing it and in the fornnnumber, and arrange,-

ment of parts of the preferred embodiment/of it maybe made'within the spirit and scope thereof. r

1 What is'claimed is: Y

- A hob-like tool having a cylindrical bodyportion and two rows of like teeth adjacently dis- ,posed and helically positioned on the surface of the body portion, certain ofthe teeth of each' row increasing in height fr m starting points "diametrically disposed.

n 2. A hob-like tool having a cylindrical body portionand two, rows of like teeth adjacently-disposed and helicallypositioned on the surface of I 5' the body portion, c'ertain'of the teeth of each row increasing in height from starting points: diametrically disposed, the end teeth of the-rows being complementary in formflto the space to be out thereby.- V

40 3.A hob-flike tool having a, ylindrical hody portion and two rows oflike teeth helically disposed on the surface thereof, the teeth at'the JOSEPH c. DRADER. 

